1. Field of the Invention
The present invention relates to a contact probe.
2. Description of Related Art
In a coordinate measuring machine, a scanning measurement is performed by bringing a scanning probe into contact with a surface of a measured object. When using an elastic hinge in a guide mechanism (in three axis directions of X, Y, Z) of the scanning probe, a measurement force of the probe is generated by a spring constant in a bending direction of the elastic hinge. The higher a rigidity of the guide mechanism is, the larger the spring constant becomes, and the larger the measurement force of the probe becomes. When the measurement force of the probe becomes large, certain influences are increased, such as an influence from a frictional force generated between a workpiece and a stylus during measurement and an influence from bending of the stylus mounted on the probe. As a result, highly accurate measurement becomes difficult.
By contrast, a technique of stabilizing the measurement force is known, in which fluctuation of the measurement force of a detector is inhibited by detecting and controlling the measurement force (Japanese Patent Laid-open Publication No. 2010-286475).
In addition, a technology is proposed for a measuring device using an elastic hinge mechanism in which a restoring characteristic of the elastic hinge is adjusted using magnets (Japanese Patent Laid-open Publication No. H11-141537).
However, inventors of the present invention have discovered an issue, as discussed below, with respect to the above-noted techniques. For example, in order to adjust the measurement force, the rigidity of the spring or the elastic hinge that provides the measurement force is lowered, and when the spring constant in the bending direction becomes small, the rigidity in another direction such as twisting or curving becomes lower as well. As a result, the influence of deformation other than in the bending direction due to the measurement force becomes greater and leads to deterioration in measurement accuracy. Accordingly, to achieve high accuracy for the scanning probe, a scanning probe with high rigidity and a small spring constant in the bending direction is required.
By contrast, in the technique disclosed in Japanese Patent Laid-open Publication No. 2010-286475, though the measurement force is adjustable, controlling the measurement force generates heat, which affects the form measuring machine in the form of thermal deformation and the like and leads to a decrease in measurement accuracy. In addition, electrical noise is generated by executing control of the measurement force, which leads to a further decrease in measurement accuracy. Furthermore, a need to mount a controller on the form measuring machine increases costs of the form measuring machine.